Subjects will complete a baseline eucaloric study day. Following this, subjects will be randomized to complete 3 days of overfeeding (150% of baseline eucaloric energy requirements) or 3 days of underfeeding (50% of baseline eucaloric energy requirements). After completing one of these study arms, subjects will cross-over and complete the second arm. All study arms will be separated by two weeks. 24-hour energy expenditure will be measured 3 times during each of 3 day periods. We hypothesize that the impact of over or underfeeding on EE will be evident after 24-hours and will be comparable to 72 hour EE.